Time and Date: 13:15 - 14:55 on 12th June 2018
Chair: Shuyu Sun
| ALE Method for a Rotating Structure Immersed in the Fluid and Its Application to the Artificial Heart Pump in Hemodynamics [abstract]
Abstract: In this paper, we study a dynamic fluid-structure interaction (FSI) problem involving a rotational elastic turbine, which is modeled by the incompressible fluid model in the fluid domain with the arbitrary Lagrangian-Eulerian (ALE) description and by the St. Venant-Kirchhoff structure model in the structure domain with the Lagrangian description, and the application to a hemodynamic FSI problem involving an artificial heart pump with a rotating rotor. A linearized rotational and deformable structure model is developed for the rotating rotor and a monolithic mixed ALE finite element method is developed for the hemodynamic FSI system. Numerical simulations are carried out for a hemodynamic FSI model with an artificial heart pump, and are validated by comparing with a commercial CFD package for a simplified artificial heart pump.
|Pengtao Sun, Wei Leng, Chen-Song Zhang, Rihui Lan and Jinchao Xu
| Free Surface Flow Simulation of Fish Turning Motion [abstract]
Abstract: In this paper, the influence of depth from the free surface of the fish and turning motion will be clarified by numerical simulation. We used Moving-Grid Finite volume method and Moving Computational Domain Method with free surface height function for numerical simulation schemes. Numerical analysis is performed by changing the radius at a certain depth, and the influence of the difference in radius is clarified. Next, analyze the fish that changes its depth and performs rotational motion at the same rotation radius, and clarify the influence of the difference in depth. In any cases, the drag coefficient was a positive value, the side force coefficient was a negative value and the lift coefficient was a smaller value than drag. Analysis was performed with the radius of rotation changed at a certain depth. The depth was changed and the rotational motion at the same rotation radius was analyzed. As a result, it was found the following. The smaller radius of rotation, the greater the lift and side force coefficients. The deeper the fish from free surface, the greater the lift coefficient. It is possible to clarify the influence of depth and radius of rotation from the free surface of submerged fish that is in turning motion on the flow.
|Sadanori Ishihara, Masashi Yamakawa, Takeshi Inomoto and Shinichi Asao
| In-Bend Pressure Drop and Post-Bend Heat Transfer for a Bend with a Partial Blockage at its Inlet [abstract]
Abstract: The full paper describes a three-part numerical investigation of fluid flow and heat transfer in a bend situation that has not been studied in the past. The investigation is motivated by interest in how downstream fluid-flow and heat transfer processes are affected by upstream flow disturbances. The investigated physical situation is a 90o pipe bend fitted with a wall-adjacent obstruction that partially blocks the flow cross section. The first phase of the work consisted of comparing results of numerical simulations with experimental data. The second phase of the paper is focused on determining the impact of the inlet flow distribution on the pressure drop in the bend proper and in the attached pipe. Heat transfer in a straight pipe situated downstream of the bend exit is the focus of the third and the most significant section of the paper. The heat transfer results are reported in terms of the circumferentially averaged Nusselt number displayed as a function of position along the pipe for Reynolds numbers ranging from 100 to 10,000. Each set of simulations consisted of cases with two different bend radii, each being simulated for six different Reynolds numbers between 100 and 10,000. There were four different sets, ranging from no blockage to as high as 60% blockage, all created using an orifice situated at the same position right before the start of the bend. It was found that the disturbances caused by the blockage significantly enhance the Nusselt number values. As expected for Nusselt numbers in the section of pipe after the bend, the numbers are higher for higher Reynolds number flows. Nusselt numbers increase non-monotonically with increase in blockage upstream of the flow, possibly due to jet-like flow patterns that develop as a result of increased blockage. A rather unsuspected result is that Nusselt numbers are seemingly more affected by the sharpness of the bends than the blockage ratio such that increasing the sharpness of the pipe bend increases the Nusselt number right after the bend more than increasing the blockage ratio does. Another interesting phenomenon demonstrated in these numerical investigations is the existence of plateaus in what was expected to be monotonic decrease in Nusselt numbers along the straight sections of pipes after the bend, specifically in high Reynolds number flows. Given that this cannot be explained by existing understanding of heat transfer in pipe bends, experimental verification of this phenomenon would be the logical next step in understanding heat transfer in pipe bends.
|Abhimanyu Ghosh, John Gorman, Ephraim Sparrow and Christopher Smith
| Computational Studies of an Underground Oil Recovery Model [abstract]
Abstract: The modified Buckley-Leverett (MBL) equation describes two-phase flow in porous media, and it is a prototype for modeling the underground oil recovery process. In this paper, we extend the second and third order classical central schemes for the hyperbolic conservation laws to solve the MBL equation which is of pseudo-parabolic type. The MBL equation differs from the classical Buckley-Leverett (BL) equation by including a balanced diffusive-dispersive combination. The classical BL equation gives a monotone water saturation profile for any Riemann problem; on the contrast, when the dispersive parameter is large enough, the MBL equation delivers non-monotone water saturation profiles for certain Riemann problems as suggested by the experimental observations. Numerical results in this paper confirm the existence of non-monotone water saturation profiles consisting of constant states separated by shocks.
| Circular Function-Based Gas-kinetic Scheme for Simulation of Viscous Compressible Flows [abstract]
Abstract: A stable gas-kinetic scheme based on circular function is proposed for simu-lation of viscous compressible flows in this paper. The main idea of this scheme is to simplify the integral domain of Maxwellian distribution func-tion over the phase velocity and phase energy to modified Maxwellian func-tion, which will integrate over the phase velocity only. Then the modified Maxwellian function can be degenerated to a circular function with the as-sumption that all particles are distributed on a circle. Firstly, the RAE2822 airfoil is simulated to validate the accuracy of this scheme. Then the nose part of an aerospace plane model is studied to prove the potential of this scheme in industrial application. Simulation results show that the method presented in this paper has a good computational accuracy and stability.
|Zhuxuan Meng, Liming Yang, Donghui Wang, Chang Shu and Weihua Zhang